RSP microcode switches are extremely slow -- they're designed to be programmed once when the game boots up, but some games switch back and forth between a 2D an

RSP microcode switches are extremely slow -- they're designed to be programmed once when the game boots up, but some games switch back and forth between a 2D and 3D microcode during different modes. So they're not like shaders in that sense -- shaders are designed to be switched every frame. And keep in mind that the RSP doesn't handle blending. The RSP can kind of be compared to a vertex shader, and the RDP is the fixed-function unit that handles rasterization, interpolation, and blending. It's "programmable" in a glTexEnv sense, but you can't upload your own code.